The assignee of the present invention, Setco Sales Company, owns U.S. Pat. Nos. 5,727,095, 5,980,115 and 6,217,219 B1, all of which are entitled “Bearing Seal With Uniform Fluid Purge,” and directed to a unique bearing seal which has proved tremendously successful in increasing the reliability of spindles. Setco sells this patented bearing seal under the trademark AIRSHIELD. These Setco patents are incorporated herein by reference, in their entireties.
According to one aspect of the prior invention, as disclosed in the three above-cited patents, the bearing seal includes an annular cap located at a first end of a bearing housing, where a shaft exits therefrom. The cap has an internal surface which defines an annular internal volume, and a passage formed therethrough which tangentially intersects the annular volume. This structure allows pressurized purge fluid to be supplied to the annular volume via the passage, to create a circumferentially uniform fluid pressure within the annular volume. This circumferentially uniform pressure prevents ingress of contaminant materials within the bearing.
This prior invention has significantly increased spindle reliability, by reducing downtime caused by failed bearing seals. Such downtime can have critical adverse effects on overall spindle efficiency and throughput.
These prior patents disclose several embodiments for achieving the critical benefits of this prior invention. Moreover, these prior patents expressly suggest that the benefits of that prior invention can be obtained in retrofit situations, where an in-place spindle with a failed bearing seal requires the retrofitting of a new bearing seal. These prior patents suggested some general details of how such a retrofitted bearing seal could be achieved. However, those prior patents did not disclose or suggest a specific structure for achieving the benefits of the prior invention with a wide variety of spindles of various size and shape.
For these reasons, Setco developed a second generation version of this type of bearing seal, i.e. a bearing seal with circumferentially uniform fluid pressure, which achieved certain advantages by using an annular cartridge having connectable stator and rotor sections. This second generation bearing seal was the subject of Setco's U.S. Pat. No. 7,090,220, entitled “Cartridge-Type Bearing Seal For Machine Tool Spindle,” which is expressly incorporated by reference herein, in its entirety. This cartridge type bearing seal facilitated the retrofitting of bearing seals on in-place spindles, readily accommodated various sizes and shapes of spindles, and did so in a simple and cost-effective manner. This second generation bearing seal also increased the availability, for a wide range of bearing seals, of the uniform air purge feature that was achieved with the original invention.